the only one i would recommend is the one from JB Prince, and it is 14.5” diameter and 18” lenght. the brand is matfer and it is from france.
i don’t recommend a traditional balloon whisk of those dimensions. it will be very very heavy and the wires pretty thick. it will be hard and heavy on your hands and on the batter. the JB prince one is lightweight and really the ultimate tool for folding on the KA 5 or 6